on the Germination of Plants. 317 



this physical cause alone. But to this, I think, it may be an- 

 swered, 1st, That it is scarcely probable, if the radicle is en- 

 dowed with a specific power, so active under particular circum- 

 stances, that its ordinary and more important direction down- 

 wards, is left to a mere physical cause, whilst the other power 

 is totally inactive. 26?^, I have seen the radicle of a bean of 

 less specific gravity than water, and, in that case, I should think 

 the pea ought to ascend if immersed in water. Sdli/, A radicle, 

 in the 6th and 7th experiments, even whilst descending, appears 

 to raise, or at least resist a weight, probably considerably 

 greater than its own when under water, and, therefore, more 

 than the actual amount of the cause to which the eff'ect is as* 

 signed. 



4. The power of the radicle, which I have thus endeavoured 

 to show to be distinct from gravitation, I can alone ascribe to 

 vegetable life. What is the nature of this supposed vital ac- 

 tion, or in what way it operates, I am totally unable to explain, 

 nor is it my object here to propose any new theory, to explain 

 this phenomenon of germination ? 



If what has been advanced has rendered it probable that 

 these motions do not depend on mere physical causes, but 

 are truly vital actions, it can only be considered as in some 

 measure clearing away the obstacles to the future prosecution 

 of this subject, which still remains an interesting field for future 

 inquiry. 



M. Du Hamel made many attempts to oblige the plume and 

 radicle to assume directions contrary to the usual course of na- 

 ture *. In one instance, an acorn was fixed between two wet 

 sponges, so that the radicle was upwards, and the plume down- 

 wards ; but this expedient was not successful. The experiments 

 which I have described not only prove the possibility of this, 

 the radicle of a mustard-seed having been made to grow up- 

 wards into a sponge (Exper. V.) ; but appear also to show why 

 this indefatigable experimenter failed in this and other similar 

 experiments. 



Edinburgh, January 22. 1829. 



• System of PhysioL Botany, by the Rev. P. Keith, vol. ii. p. 23. 

 JANUARY MARCH 1829. Y 



